Temperature indicators are already known using thermosensitive inks composed of thermochromic liquid crystals. Their technology is largely described in the review Handbook of Thermochromic Liquid Crystal Technology, Hallcrest 1991. Such temperature indicators are constituted by a substrate comprising several distinct juxtaposed zones which are each covered by a thermosensitive material reacting for each zone at a predetermined temperature. Such temperature indicators comprise as many zones, and consequently as there are many sensors, as measurable temperature steps. They must thus comprise a large number of sensors in order to be able to indicate a significant range of temperatures such as, for example, 30 sensors for a temperature measurement from 0.degree. C. to 30.degree. C. with a resolution of 1.degree. C. per step. When this type of temperature indicator must be exhibited on an element having a small surface, such as a watch or clock dial as described in the British patent application GB-A-2,135,081, for example, the readability becomes poor because of the substantial number of sensors relative to the dimensions of a watch dial which requires that each sensor have a very small individual surface.
The invention seeks to overcome this drawback in proposing a temperature indicator permitting a relatively precise temperature measurement over a wide temperature range with a reduced number of zones having large individual surfaces.